1. Field of Invention
The present invention relates to a control system for an active vibration isolation support system which supports, on a vehicle body, an engine that can selectively switch between a first running state and a second running state which differ in the number of cylinders that are permitted to operate. The control system includes a control device for controlling an actuator of the active vibration isolation support system according to a vibrational state of the engine so as to suppress transmission of vibration from the engine to the vehicle body.
2. Description of Related Art
Japanese Patent Application Laid-open No. 2003-113892 discloses a device in which a vibrational state of an engine is estimated from an angular acceleration of a crankshaft of an engine, and operation of an actuator of an active vibration isolation support system is controlled based on the vibrational state. In this device, if the engine vibration is large and it is easy to estimate the phase (for example, during selective cylinder operation in which only a subset of all cylinders is permitted to operate), the operation of the actuator is controlled based on the estimated phase for the engine vibration, whereas if the engine vibration is small and it is difficult to estimate the phase (for example, during all-cylinder operation), the operation of the actuator is controlled based on a preset phase for the engine vibration.
In some V6 engines, the operation can be switched between a selective cylinder operation state in which the engine runs as an in-line three cylinder engine with a bank on one side made non-operational, and a selective cylinder operation state in which the engine runs as a V4 engine with one cylinder in each of the two banks made non-operational. In this case, there are three running states, that is, V6 all-cylinder operation, L3 selective cylinder operation, and V4 selective cylinder operation. When switching among these three running states, the vibrational state prior to the switch continues due to the inertia of the engine for approximately one cycle of vibration after the switch. If the control of the active vibration isolation support system for the vibrational state prior to switching between running states is continued, after the switch, for a period corresponding to only one vibration cycle, the vibrational state during the switch can be improved.
However, depending on the combination of a running state prior to switching between running states of the engine and a running state subsequent to the switch, there is a case where the vibrational state prior to the switch may continue for a longer period of time after the switch. In this case, it is desirable that control of the active vibration isolation support system corresponding to the vibrational state prior to the switching between running states is continued after the switch for a longer period than the period corresponding to one vibration cycle.